Foreign key constraint name is weird

[sir4ur0n]

Hello,

I am unsure if this is intentional - in which case this is a request for improvement - or not - in which case this is a bug report.

The foreign key constraint name is weird: it seems that the (mandatory) constraint name passed in the quasi quoter is appended with no separator (e.g. _) to the FK table name.

FYI I use:

• Stack with resolver lts-16.5, so Persistent 2.10.5.2 and Persistent Template 2.8.2.3
• PostgreSQL 11.8

To reproduce:

share
  [mkPersist sqlSettings, mkMigrate "migrateAll"]
  [persistLowerCase|
  FooBar
      foo String
      bar Bool
      Primary foo bar
      deriving Show
  FooBarBaz
      foo String
      bar Bool
      baz Int
      Primary foo bar baz
      Foreign FooBar fk_something foo bar
      deriving Show
|]

The foreign key constraint is named foo_bar_bazfk_something, i.e. it appends the table name foo_bar_baz to the provided QQ name fk_something with no separator.

While I don't mind being forced to prefix with the table name foo_bar_baz, I don't understand why there isn't at least a separator _ between the table name and the given suffix (so it would be foo_bar_baz_fk_something). And it's illegal (doesn't compile) to write Foreign FooBar _fk_something foo bar.

What do you think?

Cheers!

[parsonsmatt]

Great catch! I did not know this either.

To fix this, we'll want to introduce a field on the relevant Settings datatype that accepts a "foreign key first character" - eg mkPersistSettingsTableSeparator :: Maybe Text - with a default value of Nothing. Users can opt in to Just "_" or similar. This would be a breaking change, but could land in 2.11 or 2.12.

[parsonsmatt]

It should also be pretty easy to modify the parser to accept a leading underscore, which would not be a breaking change